JP2003208371A - Routing method using name resolution and its system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a routing method using name resolution and its system for enabling derivation to the optimal edge server by performing request routing in consideration of a position of a client to the client of a mobile network. <P>SOLUTION: A local DNS (domain name system) serve 2a manages a forwarding table 21 provided with a binding cache consisting of a set of a home address and a care of address of the client 1 and an IP (Internet protocol) address of an external local DNS server 2b as a DNS server of an external network. Then, when a request of the name resolution is issued from a resolver of the client 1, the local DNS server 2a transfers the request of the name resolution to the external local DNS server 2b by using the forwarding table 21. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a routing method and system using name resolution. In particular,
The present invention relates to a routing method and system using name resolution capable of delivering contents to a client of a mobile network by routing considering the position of the client.

[0002]

2. Description of the Related Art At present, a content distribution network (CDN) that distributes content to a server (edge server) in the vicinity of a client in advance as the access network becomes wider and the capacity of Web content becomes larger.
livery network) is attracting attention. Request Routing System (RRS)
m) is a component of the CDN, and is a system for guiding the client's content request to the edge server having a copy of the content. The basic functions of the request routing system are:
There are the following two. 1) Direct the client to an edge server that can respond to the request. 2) Guide the client to the edge server that can provide the best service.

At present, there is a "DNS-base" as a request routing system used when distributing contents provided on a website using a CDN.
There is a conventional technique called “d” request routing system. The conventional technique is a DNS (Domain Name Syst).
em) is a method used to guide the client. In this case, one or more domain names are given to the request routing system. This domain name is then used to guide the client's request and is used as part of the URL. In addition, this method has already been widely used on the Internet.
Since NS is used as a base, it can be used from anywhere on the Internet.

[0004]

By the way, the mobile I
If the above conventional technique is applied to a mobile network such as a P network, there are the following problems. In other words, the client is a DNS server (hereinafter, referred to as “DNS server” in the area (home network) to which the client originally belongs in the mobile network.
Since the IP address of "home / local / DNS" is known in advance, even if this client moves to another area in the mobile network, the home / local / DNS server and the edge server in the home network Can be used.

However, in that case, in the conventional technique, since the edge server is determined based on the IP address of the home / local / DNS server, it may not be the optimum edge server for the client in the destination area. is there. That is, there is a problem in that the destination client receives the content distribution from the edge server existing in the home network far away from the client, not from the edge server existing in the area to which the client currently belongs. .

[0006] Further, with respect to the edge server, a problem called triangle problem may occur.
That is, the client is
Although the content is acquired from the edge server guided by the system, when the content is transmitted to the client in the destination area, the communication between the client and the edge server does not become a linear path, and the client In some cases, the home network and the edge server may have a triangular communication path, that is, a communication path that makes a large detour, which may put pressure on the network band between the home network and the external network.

The present invention has been made in view of the above-mentioned circumstances, and is directed to a client of a mobile network.
It is an object of the present invention to provide a routing method and a system using name resolution that can guide an optimal edge server by performing request routing considering the position of a client.

[0008]

In order to achieve the above object, according to the invention of claim 1, a client, which is a terminal that moves in a mobile network, and a plurality of contents distributed in the network to distribute contents are provided. A routing method for selecting a communication path to an edge server to be distributed to the client, wherein, for each area of the network, a local DNS server that constitutes a DNS server of the area and the edge server are arranged, and the client A home / local DNS server that is a DNS for the area is placed in the home network, which is the area to which the
When the authoritative DNS server that manages the table in which the addresses of the NS server and the edge server are associated with each other is arranged, the home / local DNS server receives the movement information of the client, and based on the movement information, the client The address of the local DNS server in the destination area is recorded, and is recorded when the client requests the home / local DNS server for the name resolution necessary for accessing the content. Based on the address, the request is transferred to the local DNS server in the destination area, and the local DNS server in the destination area inquires of the authoritative DNS server about the address of the edge server corresponding to the content, The authority DNS server is the recorded Based on the address, the address of the edge server in the destination area is transmitted to the local DNS server in the area, and the local DNS server in the destination area transmits the received address to the client. To do. According to the invention,
In the "DNS-based" request routing system, when a client moves from a home network to another area (external network),
The client is guided to the edge server of the external network based on the IP address of the DNS server of the external network, not the IP address of the DNS server (DNS server of the home network) that has made the name resolution inquiry of the edge server. Therefore, mobile IP
It is possible to guide the client of the network to the optimum edge server.

According to the second aspect of the invention, the first aspect is
The movement information of the client described in 1. includes a home address which is an address of the client on the home network and a care-of address which is an address in an area of the movement destination of the client. .

According to the invention described in claim 3, claim 1
Alternatively, when the home / local DNS server described in 2 records the address of the local DNS server in the area to which the client moves, the recorded address and the care-of address or the area managed by the authoritative DNS server are set. At least one of the addresses of the authority zones shown is recorded in association with each other.

According to the invention described in claim 4,
The routing method according to any one of claims 1 to 3, wherein the edge server automatically selects a shortest route as a communication route between the edge server and the client.

In order to achieve the above-mentioned object, in the invention according to claim 5, a client which is a terminal moving in a network, and an edge server which is arranged in each area of the network and distributes contents to the client are provided. Which is one of the local DNS server and a local DNS server which is arranged in each area of the network and constitutes a DNS of the area, The home / local DNS server that forms the DNS of the home network, which is the area to which the server originally belongs, and the address assigned to the edge server,
Authority to manage in a table associated with the local DNS server in the same area, and to reply to the inquiry of the address of the edge server corresponding to the content issued from the local DNS server by using the table D
An NS server, wherein the home / local DNS server records the address of the local DNS server in the area to which the client has moved, and the DNS of the recorded address for the request for the content from the client. And the function of transferring to a server.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The present invention is based on the conventional "DNS-bas".
The ed "request routing system is improved to be a request routing system applicable to mobile networks such as mobile IP networks.

A. Configuration of Embodiment FIG. 1 is a conceptual schematic diagram showing a request routing system according to an embodiment of the present invention. In the figure, a client 1 is a mobile terminal that receives distribution of content. The mobile IP network is divided into a plurality of areas, and the client 1 moves in each area. In this embodiment, from the home network, which is the area to which the client 1 originally belongs, the client 1
Consider a case where the client 1 moves to an external network, which is an area to which the client moves. Also, client 1
The IP address of is (192.168.1.100). The resolver of the client 1 is set with the IP address (192.168.1.2) of the local DNS server existing in the home network. The resolver is software that performs name resolution between an IP address and a URL (domain name), and is built in the client 1 (mobile terminal). A home agent (HA), which is a server that provides and manages mobile IP, is arranged in the home network. The home agent sequentially sends the mobile information of the client 1 to the local DNS server existing in the home network. The home agent preferably supports a route optimization extension function (RO: Route Optimization) that automatically selects the shortest route as the communication route of the client in the home network.

The local DNS servers 2a and 2b make an inquiry about the name resolution (process for identifying the domain name and the IP address) of the edge server to the server (authoritative DNS server 6) that inquires about the name resolution. It is a server. The local DNS server 2a exists in the home network, and the local DNS server 2b
Exist in the external network and have IP addresses (192.168.1.2) and (192.168.2.
2) is assigned. Further, the local DNS server 2a includes a forwarding table (described later) 21.

The edge servers 3a and 3b are servers that deliver contents to the client 1. The edge server 3a exists in the home network, the edge server 3b exists in the external network, and the IP addresses (192.168.1.3) and (192.16) respectively.
8.2.3) is assigned.

The Internet, which is a network different from the mobile IP network, has an origin server 4,
Root DNS server 5, authoritative DNS (Authoritative DN)
S) The server 6 is arranged. Origin server 4
The Web server is a server that has an original of the content distributed to the client 1. The contents of the origin server 4 are usually sent to the edge servers 3a and 3b, which are mirror servers, respectively, and delivered to the client 1 from the edge server 3a or the edge server 3b. The root DNS server 5 is the highest DNS server located above the local DNS servers 2a and 2b. Authoritative DNS
S) The server 6 connects the client 1 to the edge servers 3a, 3
It is a DNS server that has authority for name resolution of each edge server 3a, 3b when guiding to b. Authority DN
The S server 6 is the IP of the local DNS servers 2a and 2b.
The “request / routing / routing” that consists of the address and the IP address of the corresponding edge server 3a, 3b.
It has a table. Note that the origin server 4, the root DNS server 5, and the authoritative DNS (Authoritative
The DNS) server 6 may be arranged in any network.

B. Operation of Embodiment Next, operation of the request routing system shown in FIG. 1 will be described. First, as a pre-process, the resolver of the client 1 is provided with an IP address (192.
168.1.2) is set. Then client 1
Is moved from the home network to the external network. Then, the client 1 receives the desired content on the Web browser in order to receive the desired content.
Enter the RL (eg, http://www.sp.foo.com/movie.mpeg) or click the link.

Then, the resolver of the client 1 requests the local DNS server 2a for name resolution of the domain name (for example, www.sp.foo.com) of the above URL. In this name resolution, the process of converting a domain name into an IP address is repeated, that is, recursively. Upon receiving the request, the local DNS server 2a uses the forwarding table 21 to transfer the name resolution request to the external local DNS server 2b of the external network in which the client 1 is present (reference numeral). Here, data is recorded in the forwarding table 21 as follows.

First, the local DNS server 2a obtains the movement information of the client 1 (information consisting of a pair of home address and care-of address, called "binding cache") from a home agent (not shown) in advance. Request. Here, the home address is
This is the address of the client 1 on the home network of the client 1 and does not change. The care-of address is the address of the client 1 in the area to which the client 1 has moved, and changes every time the area is moved. This request allows the local DN
The S server 2a obtains a response (binding update message) from the home agent as movement information. This movement information has an expiration date so that an update request for outdated information can be issued.

Then, the local DNS server 2a, based on the response, binds the client 1 with
The cache and the IP address of the local DNS server 2b in the destination area (external network) of the client acquired by the method described later are recorded in the forwarding table 21. The care-of address recorded in the forwarding table 21 (hereinafter referred to as "pointing address") may not always match the care-of address sent from the home agent momentarily. That is, a tight lag may occur until the pointing address is updated with the latest care-of address sent from the home agent. Then, the local DNS server 2a uses the forwarding table 21 to transfer the name resolution request to the external local DNS server 2b.

A specific example of the forwarding table 21 in which the data is recorded in this way will be described with reference to FIG. In each record of the table, movement information of different clients (a, b1, b2, b3) is recorded. The "pointing address" field in the table indicates the pointing address described above. The "authority zone" field indicates an address to be managed by the local DNS server 2b arranged in the destination area of the client, and is (6.128.133.in-ad).
dr. arpa) is “133.128.6.1” to “1.
The local DNS server 2b manages clients having addresses up to 33.128.6.254 ". Details of the authority zone will be described later.

In the case of the clients b1, b2 and b3, the pointing address is DHCP (Dynamic Host C
onfiguration Protocol). Here, the dynamic allocation method is a method in which, when a client logs in to a network, the DHCP server allocates one of the prepared IP addresses to the client. Therefore, even if the client continues to exist in the same area, the pointing address assigned to the client may change due to the login / logout operation of the client.

Further, the "external local DNS" field is an external local DNS of the destination area of the client.
The IP address of the server is shown. "External local D
The procedure for recording “NS” will also be described later. "expiration date"
The field indicates the expiration date of each record and is for urging the data to be updated.

Based on the name resolution request transferred by the above forwarding table, the external local DNS
The server 2b requests the root DNS server 5 for name resolution of the domain name (reference numeral). In this name resolution, the process of converting a domain name into an IP address is repeated, that is, iteratively performed. Then, the root DNS server 5
Responds to the external local DNS server 2b with the IP address of the authoritative DNS server 6 having the authority to resolve the domain name (reference numeral).

Next, the external local DNS server 2b
Request the iterative name resolution from the authoritative DNS server 6 (code). Authority DNS server 6 that received this request
Selects a predetermined edge server 3b based on the request routing table and returns its IP address to the external local DNS server 2b (reference numeral). Here, the request routing table is a table in which the IP addresses of the local DNS servers 2a and 2b and the IP addresses of the edge servers 3a and 3b in the same area are recorded in association with each other. And authority DNS
The server 6 requests the external local DNS server 2
b address is referred to from the request routing table, and the corresponding edge server (192.168.168.
Specify the IP address of 2.3). External local DN
The S server 2b returns the IP address (192.168.2.3) of the edge server 3b to the resolver of the client 1 (reference numeral). From the above, W of client 1
The eb browser is the edge server 3b (http://192.168.2.3/video.aw) of the external network which is the nearest area.
t) can be accessed to receive the desired content distribution (code).

Next, the procedure for the home / local DNS server to create and manage the forwarding table will be described with reference to FIG.

In FIG. 2, the local DNS server 2a
Is the client 1 obtained from the home agent
Of the binding cache of the home agent (H) before the expiration date (step S1), the home agent (H
A) is transmitted (step S2). That is, request the latest binding cache.

After that, the local DNS server 2a judges whether or not the binding update is received from the home agent (step S3). The binding update is update information of the binding cache. If the binding update is not received in step S3, it means that the client 1 exists in the home network, and thus the processing of the local DNS server 2a ends.

When the binding update is received in step S3, it means that the client 1 has moved from the home network to the external network. In this case, the local DNS server 2a
Determines whether the care-of address in the binding cache and the home address match (step S
4). If the care-of address and the home address match in step S4, it means that the client 1 has returned from the external network to the home network.
The processing of the local DNS server 2a ends.

If "No" in step S4, it is again determined whether the care-of address of the client 1 and the home address match (step S5). Step S
If the care-of address and the home address match in 5, the client 1 has returned from the external network to the home network, and the processing of the local DNS server 2a ends.

If the care-of address and the home address do not match in step S5, it means that the client 1 exists in the external network. Therefore, the local DNS server 2a uses the forwarding table 2
It is determined whether the pointing address of 1 and the care-of address acquired from the home agent match (step S6). In step S6, pointing
If the address and the care-of address match, the current movement information of the client 1 has already been stored in the forwarding table 21, so the processing of the local DNS server 2a ends.

If the pointing address and the care-of address do not match in step S6, the current movement information of the client 1 is the forwarding table 21.
May not be accumulated in. So local D
The NS server 2a determines whether the care-of address of the client 1 is included in the authority zone of the forwarding table 21 (step S7). Here, the data recorded in the authority zone does not change unless the client 1 moves to another area. Therefore, step S7
When the care-of address of the client 1 is included in the authority zone, it means that the area in which the client 1 is present has not changed since the previous update of the forwarding table 21. That is, in this case, since the care-of address of the client 1 is dynamically assigned by DHCP, it is different from the last time the forwarding table 21 was updated, but in reality, the client 1 is in the same area as the last update. Indicates that you are inside. Therefore, since the current movement information of the client 1 has already been accumulated in the forwarding table 21, the processing of the local DNS server 2a ends.

In step S7, the case of "No" is a case where the current movement information of the client 1 is not stored in the forwarding table 21, and the movement information of the client 1 is first stored in the forwarding table 21.
Or when the client 1 moves to another area (external network). Therefore,
Forwarding the current movement information of client 1
The following processing (steps S8 to S10) for accumulating in the table 21, that is, for creating a new entry in the forwarding table 21 is performed.

First, the local DNS server 2a uses the care-of address of the client 1 to the address of the authority zone in the area to which the client 1 has moved and the external local DNS.
A name resolution request for the address of the S server is executed (step S8). Since the address of the authority zone of the destination area is known by the external local DNS server existing in the area, the name resolution request is issued by the external local DNS server (eg, the external local DNS server having the authority of the name resolution request).
External local DNS server 2 to which client 1 is moved
It is executed as an iterative reverse lookup name resolution request that repeatedly executes the process of finding the IP address of b). Then, the local DNS server 2a inquires the address of the authority zone from the external local DNS server based on the address in step S8 (step S9).

Thereafter, the local DNS server 2a forwards the care-of address of the client 1, the address of the authority zone acquired in steps S8 and S9, and the IP address of the external local DNS server.
Described in the table 21 (step S10).

Next, the client 1 is the edge server 2
A processing procedure when receiving desired contents from a and 2b will be described with reference to FIG. In order for the client 1 to receive the desired content distribution, the client 1
When there is a name resolution request from the resolver, the home / local DNS server 2a performs the processing shown in FIG.
First, the home / local DNS server 2a receives a name resolution request from the resolver (step S21). Then, the home / local DNS server 2a refers to the binding cache, which is information consisting of the home address and the care-of address of the client 1 (step S22), and determines whether or not there is a binding cache (step S23). .

If it is determined in step S23 that there is no binding cache, it means that the client 1 has not moved from the home network or the expiration date in the forwarding table 21 has expired. The server 2a sends a warning (binding warning message) to the home agent (step S2).
4).

After that, the home / local DNS server 2
The a determines whether it has received a binding update from the home agent (step S25). Here, if the binding update is not received, it means that the client 1 exists in the home network, and therefore the home / local DNS server 2a.
Performs iterative name resolution (step S26).
Then, the home / local DNS server 2a transmits the execution result of the iterative name resolution to the resolver, and ends the processing (step S27).

If the binding update is received in step S25, it means that the client 1 does not exist in the home network. Therefore, the home / local DNS server 2a sends the forwarding
It is determined whether the pointing address of the table 21 and the care-of address of the client 1 match (step S28).

In step S28, when the pointing address and the care-of address do not match, the home / local DNS server 2a determines whether the care-of address of the client 1 is included in the authority zone of the forwarding table 21 ( Step S29). In step S29, if the care-of address is not included in the authority zone, it means that the client 1 has moved to another area, so it is necessary to update the record of the forwarding table 21. So, home / local DNS
The server 2a repeatedly executes a name resolution request for obtaining the address of the authority zone of the destination area of the client 1 and the address of the external local DNS server from the care-of address of the client 1 (step S30). Similar to step S8 of FIG. 2, the name resolution request is an iterative reverse process in which the process of searching for the IP address of the external local DNS server (the foreign local DNS server 2b of the moving destination) having the authority of the name resolution request is repeatedly executed. Executed as a name resolution request. Next, in step S31, the home / local DNS server 2a determines whether or not an external local DNS server has been found (step S31), and “No”.
In this case, the request is given up and the process of step S27 described later is executed.

If a local DNS server having the authority of the name resolution request is found in step S31, the home
The local DNS server 2a acquires the address of the authority zone and the IP address of the external local DNS server in the same manner as in steps S9 and S10 of FIG.
The forwarding table 21 is updated with this data (step S32). After that, the home / local DNS server 2a uses the forwarding table 21 updated in step S32 to execute the external local DNS.
The external local DNS server 2 communicates with the S server 2b and requests the name resolution request of the edge server from the client 1.
Then, the name is requested to be recursively executed (step S33). External local DNS server 2b
Sends the execution result of name resolution of the edge server to the resolver, and ends the processing (step S27). When the resolver of the client 1 receives the execution result of the name resolution of the edge server, the I of the nearest edge server 3b is received.
After acquiring the P address, the client 1 receives the desired content from the edge server 3b.

Next, a method of managing the forwarding table 21 will be described with reference to FIG. 5 in order to deal with the case where the external local DNS server 2b goes down or the server address is changed. First, the home local DNS server 2a determines the expiration date of each record recorded in the forwarding table 21 and, before the expiration date expires (step S41), issues a name resolution request for the pointing address of the record. Execute (step S42). This name resolution request is shown in FIG.
Similar to step S8 of step 1, the external local DNS server (for example, the client 1
Is executed as an iterative reverse lookup name resolution request for repeatedly executing the process of searching the IP address of the external local DNS server 2b) of the destination.

After that, the home / local DNS server 2
a is an external local DN by the process of step S42.
It is determined whether the S server is found (step S43).
If the external local DNS server is not found in step S43, it means that the client 1 exists in the home network and does not need the external local DNS server. Therefore, the home / local DNS server 2
a terminates the management processing of the forwarding table 21.

When the external local DNS server is found in step S43, the home / local DNS server 2a determines the IP address of the external local DNS server and the IP address of the external local DNS server recorded in the forwarding table 21. It is determined whether and are the same (step S44). If it is determined in step S44 that the external local DNS server is down or the server has not been changed, it is not necessary to change the contents of the forwarding table 21, and the home / local DNS server 2a does not change the contents of the forwarding table 21. The management process ends.

If it is determined in step S44 that they are not the same, it means that the external local DNS server is down or the server is changed. Therefore, the home / local DNS server 2a performs the care-of address of the client 1 and the external local DNS in the same manner as in step S10 of FIG.
Forwarding the address of the authority zone received from the server and the IP address of the external local DNS server
It records in the table 21 (step S45). As a result, when the external local DNS server 2b is down or the server is changed, a new external local DNS server 2b is created.
Even if is installed, its content is correctly updated in the forwarding table 21, so that the routing method of this embodiment already described can be executed.

Even if the edge server closest to the client is found as described above, the effect of the present invention cannot be sufficiently exerted unless the route of content transmission from the edge server to the client is optimum. For example, in FIG. 1, it refers to a problem in which the edge server is in the same area as the client but communicates with the client via another area. Therefore, it is preferable that the edge server support a route optimization extension function (RO: Route Optimization), that is, a route optimization function that automatically selects the shortest route as a communication route with a communication partner.

As described above, according to the request routing system of this embodiment, the local DNS server 2a performs request routing in consideration of the location of the client 1 with respect to the client 1 of the mobile IP network. The client 1 can be guided to the optimum edge server. For example, in FIG.
At the local DNS server 2a, when the client 1 is in the home network, the local DNS server 2a sends the content from the edge server 3a of the home network
Can be delivered to. Further, the local DNS server 2a can cause the edge server 3b of the external network to deliver the content to the client 1 when the client 1 is moving to the external network.

The request in the above embodiment
Various processes may be executed by causing a computer system to read and execute a program for realizing the functions of the routing system.

[0050]

As is apparent from the above description, according to the present invention, the home / local DNS server records the address of the local DNS server to which the client moves.
Since the name resolution request necessary for accessing the content from the client is transferred to the local DNS server of the recorded address, the client in the mobile network is routed in consideration of the position of the client. Therefore, the client can be guided to the edge server corresponding to the position of the client.

[Brief description of drawings]

FIG. 1 is a conceptual schematic diagram showing a request routing system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a process performed by a home / local DNS server.

FIG. 3 is a diagram showing a specific example of a forwarding table 21.

FIG. 4 is a flowchart showing a processing procedure for a name resolution request from a resolver.

FIG. 5 is a flowchart showing a management method of the forwarding table 21.

[Explanation of symbols]

1 client 2a local DNS server (home / local DNS server) 2b local DNS server (external local DNS
S server) 3a, 3b Edge server 4 Origin server 5 Root DNS server 6 Authoritative DNS server 21 Forwarding table

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Takahito Yoshihara, inventor             2-15-1 Ohara, Kamifukuoka City, Saitama Stock             Company CAD Research Institute (72) Inventor Hironori Horiuchi             2-15-1 Ohara, Kamifukuoka City, Saitama Stock             Company CAD Research Institute F-term (reference) 5K030 GA01 HC09 JT09 LB05                 5K067 AA34 BB04 DD17 DD57 EE02                       EE10 EE16

Claims (5)

[Claims] 1. A routing method for selecting a communication path between a client, which is a terminal that moves in a mobile network, and an edge server, which is distributed in the network and a plurality of which are distributed to the client. , For each area of the network, the DNS of that area
A local DNS server forming a server and the edge server are arranged, and a home network forming a DNS of the area is added to a home network which is an area to which the client originally belongs.
When a local DNS server is arranged and an authority DNS server for managing a table in which the addresses of the local DNS server and the edge server in the same area are associated with each other is arranged, the home / local DNS server moves the client. It is necessary for receiving information, recording the address of the local DNS server in the area to which the client has moved based on the movement information, and accessing the content from the client to the home / local DNS server. When a request for name resolution is made, the request is transferred to the local DNS server in the destination area based on the recorded address, and the local DNS server in the destination area is transferred to the authoritative DNS server. , Edge server corresponding to the content The authoritative DNS server sends the address of the edge server in the destination area to the local DNS server in the area based on the recorded address, and the local DNS server in the destination area , The received address is transmitted to the client. 2. The movement information of the client includes a home address, which is an address of the client on the home network, and a care-of address, which is an address in an area of the movement destination of the client. The routing method according to claim 1, wherein the method is a routing method. 3. The home / local DNS server manages the recorded address and the care-of address or the authoritative DNS server when recording the address of the local DNS server in the area to which the client is moved. The routing method according to claim 1 or 2, wherein at least one of the addresses of the authority zone indicating the area is recorded in association with each other. 4. The routing method according to claim 1, wherein the edge server automatically selects a shortest route as a communication route between the edge server and the client. 5. A routing system for selecting a communication path between a client, which is a terminal moving in a network, and an edge server, which is arranged in each area of the network and distributes contents to the client, A local DNS server which is arranged in each area of the network and constitutes a DNS of the area, and which constitutes one of the local DNS servers and a DNS of a home network which is an area to which the client originally belongs. A home / local DNS server and an address assigned to the edge server are managed in a table associated with the local DNS server in the same area, and the edge server corresponding to the content issued from the local DNS server is managed. To inquire about the address, An authoritative DNS server for replying using the table, the home / local DNS server having a function of recording the address of the local DNS server in the area to which the client is moved, and accessing the content from the client. A function of forwarding a name resolution request necessary for doing so to the DNS server of the recorded address,
A routing system comprising: